﻿// Jinx AJAX Framework
// Copyright (C) 2008 Blake Hegerle
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Diagnostics;
using Core;

namespace Formality.FormalSystem.Reasoning
{
    public static class JustificationSearch
    {
        public static Justification Follows(this Proposition Goal, Proposition[] Premises)
        {
            return Goal.Follows((from p in Premises select Tuple.New(p, true)).ToArray());
        }

        public static Justification Follows(this Proposition Goal, Proposition Basis, Proposition[] Premises)
        {
            return Goal.Follows(Basis, (from p in Premises select Tuple.New(p, true)).ToArray());
        }

        public static Justification Follows(this Proposition Goal, Tuple<Proposition, bool>[] Premises)
        {
            return (from P in Premises
                    select Goal.Follows(P.Item1, Premises))
                    .FirstOrDefault(P => P != null);
        }

        public static Justification Follows(this Proposition Goal, Proposition Basis, Tuple<Proposition, bool>[] P)
        {
            var Premises = (from p in P select p.Item1).ToArray();

            var Searches = new IJustificationSearch[] {
                new VariableRenaming.Search(Basis,Goal),
                new FunctionSubstitution.Search(Basis, Goal),
                new Rewrite.Search(Basis, Goal, Premises),
                new RuleInference.Search(Goal, Basis, Premises),
            };

            foreach (var Search in Searches)
            {
                var Timer = Stopwatch.StartNew();
                var Justification = Search.Perform();
                Timer.Stop();

                if (Justification != null)
                    return Justification;
            }

            return null;
        }
    }
}
